Exhaust valve assemblies include a flapper valve that is supported on a shaft within an exhaust tube. An actuator drives the shaft to move the flapper valve within the exhaust tube to control exhaust flow. Actuators can include spring actuators, electric actuators such as motors or solenoids, or vacuum actuators, for example. The shaft is supported by bushings such that the shaft and flapper valve can pivot together about an axis.
The actuator provides a driving output to the shaft to pivot the flapper valve between an open and closed position within the exhaust tube. When the flapper valve is in the closed position, there is a tendency for the flapper valve to generate a chattering noise, which is not desirable. This chattering behavior is a result of the movement of the flapper valve, driven by exhaust pulsations, such that the shaft moves within a clearance of the bushings. This movement generates the chattering noise and can also lead to durability issues for the bushings and associated exhaust valve components.
It is know that pre-loading the shaft results in reduced valve chatter. One proposed solution has been to utilize a spring and cable assembly to preload the shaft. The spring and cable assembly is coupled to each end of the shaft. A first cable is attached to one shaft end, a second cable is attached to an opposite shaft end, and a spring couples the first and second cables to each other. The spring is resiliently biased to pull the first and second cables toward each other, such that preload forces are exerted on both ends of the shaft.
One disadvantage with this assembly is that it is difficult to package efficiently within an exhaust component. Also, the need for both shaft ends to be coupled to the spring and cable assembly further complicates the assembly process.
Thus, there is a need an exhaust valve assembly that reduces valve chatter, and which can be easily packaged within an exhaust component.